Add resolved paragraph direction to tests

Only the tests in BidiCharacterTests.txt specify the resolved direction,
so we express the non-specification by using the
neutral-direction-enum-type.

Running the tests, I noticed a small mistake I made, leading to the
wrong resolved type being emitted. The final solution is to use a proper
enum-return-type for the paragraph_level-function, which has been added
as a TODO.

Signed-off-by: Laslo Hunhold <dev@frign.de>